Compatible washlet for American Standard Champion toilet with curved back

Can anyone suggest a suitable washlet seat for the attached American Standard round-seat toilet? There is approx.1.5" of relatively flat area behind the mounting holes (mid-point) with a further 2.5" of sharply curved base behind that.
Also are there any particular washlet models I should avoid?

Thanks Terry and I will look into it.
Completely agree on the elongated bowl although as it's a rented property there is not much I can do about the round seat. Round doesn't seem to be designed for humans; not this human anyway.

I went with the Blooming Bidet and it was a good fit. Your advice worked out well.
I'm closing on a house next week and it looks like it will fit one of the toilets there and I plan to buy a new washlet seat for the other bathroom.